Bicycle generator project Freiraumschule Kritzendorf

We attached an old car alternator to a bicycle on a fixed stand. By cycling, electricity is produced. An interesting project with simple electrics on an alternative school.

We started by testing the car alternator, just to find out it was not working anymore. We had to find another one quickly from some scrap source. We had to figure out the correct wiring diagram of the alternator and some way to pre-magnetize the rotor with the field coil.

Measuring the current that’s being produced

Car alternators don’t have permanent magnets so they need a little current flowing through their field coil to get it magnetized, so when you first turn it, that bit of magnetism can induce the first output in the stator and then the alternator becomes „self-exited“. That first bit of current comes through the control lamp in the car, so we just used a small light bulb to pre-magnetize the field coil. We used a small motorcycle battery as an energy storage.

The alternator attached to the rear wheel of a bicycle

It turned out that it needs quite some force to get electricity out of the system. Some power (around 35w) is always lost in the field coil, so you need to pedal 35w before anything is coming out… Another generator with permanent magnets would be more efficient in this situation.

We had some good fun trying to get the most current and running a variety of items off the system via an Invert that creates grid-level voltage, such as a lamp, an electric blender and a laptop.

Running different loads on the self produced electricity

The Freiraumschule is the same school where I gave a wind turbine construction workshop for kids earlier in 2016.